So a friends with benefits is a touchy subject. there's the stereotype of someone always catching feelings and ruining it. This has lead to many unsuccessful attempts at having a friends with benefits.
I've had a successful friends with benefits dynamic though and some points are key.
First and foremost is being honest from the get go. Each and every relationship you get in requires a basis to start. If you start talking to someone and are honest that your intention is not to date or be together but really just to have sex occasionally then make that absolutely clear.
Second, keep the appropriate type of relationship. If you literally just want sex then only communicate when they is the goal. Dont really get all personal in those conversations.
Third, communicate. If you're no longer wanting to be friends with benefits then say that. If you are starting to catch feelings say that. You dont have to spill your guts to the other person but letting them know where you're at is important.
Any other tips please post below but these are the ones that I've found work best.